Ace Custom: Happens a lot, aided and abetted by the highly modular and modifiable nature of Imperial technology. (Indeed, both the Navy and the Legions positively encourage the practice – as long as you stick to the standard interfaces and thus do not muck up the supply chain, or drop below the baseline performance – on the grounds that they enjoy keeping their opponents in a state of perpetual confusion and disorientation with regard to what can actually be expected out of their hardware.)
This is a companion discussion topic for the original entry at https://eldraeverse.com/2016/03/19/trope-a-day-ace-custom